1. Field of the Invention
The present invention relates to an optical information processing technique using spatial Fourier transform operation, and more particularly to an optical pattern recognition technique using joint transform correlation.
2. Description of the Related Art
Optical information processings have been developed which use spatial Fourier transform operation. Typically, image correlation methods have been proposed for optical image recognition systems. Various types of optical correlators have been proposed for detecting correlation between multiple images.
For example, a Vander-Lugt optical correlator has been proposed in "Pattern Recognition with the Use of a Phase Filter in an Optical Correlation System" (Applied Physics, 58, 6 (1989).) The Vander-Lugt optical correlator, however, requires precise positioning of a hologram image, and therefore is not practically applicable.
A Joint Transform Correlator (which will be referred to as "JTC," hereinafter) has been proposed in "Fourier Transform in Optical Information Processings" (Optics, 21, 6, pp. 392-399). The Joint Transform Correlator does not necessitate the precise positioning of the hologram image, and is practically applicable. For example, Japanese Unexamined Patent Application Publication No.3-204625 has proposed one type of the JTC.